a buds 15. This is the process wherein a sperm cell unites with an egg cell to form a zygote. a. asexual reproduction b. fertilization c. pollination d. vegetative propagation 16. In sexual reproduction, sex cells are also known as b. gametes c. offspring d. spores 17. In sexual reproduction, this is the zygote's source of genetic material a a sperm and an egg cell b. egg cell only c. pollen grains and sperm d. sperm cell only 18. The following are characteristics of sexual reproduction except a gametes or sex cells from two parents unite to form a zygote b. genetically, the offspring are identical with the parents c. genetic variability of offspring helps to ensure survival even in changing environmental conditions d. the offspring are different from their parents and siblings 19. What is likely to happen when a certain species of an organism produces rapidly over time? a ecological imbalance c. overpopulation b. insufficient food and resources d. all of the above 20. Likewise, what is likely to happen when a certain species of an organism stops reproduction process? a extinction b. global warming c. habitat loss d. no effect at all​